In recent years, battery-powered portable device called tablets or phablets have seen widespread adoption. Such devices have a handwriting input function to facilitate input operation by a user. Currently, many devices have a handwriting input function capable of accepting not only input operation on the touchpanel by a finger, but also by a stylus.
When characters are input by use of a stylus on a capacitive touchpanel, there is a problem that the tip of the stylus is thick, and small characters cannot be written in comparison with a digitizer. However, small characters can be written by making the tip of the stylus thin by improving the accuracy of the touchpanel and using an active stylus having a power source (battery). Therefore, attention has focused on character input using an active stylus as a new input interface.
The active stylus has a problem in that the battery soon becomes exhausted if the stylus is always turned on and ready to write. To solve this problem, various methods for saving power such as switching between power-on and power-off by means of a side switch, etc., have been considered.
Some devices capable of input operation by use of an active stylus comprise a function of displaying a mark as a guide at the position on the touchpanel pointed to by the tip of the active stylus, which is not in contact with the touchpanel, based on a transmission signal output by the active stylus. The mark is called, for example, a hover, and the function of displaying the mark as a guide is called, for example, hovering.
It is assumed that the active stylus is shifted to a sleep state in which the transmission signal is not output during an idle period (i.e., if writing is not executed for more than a certain time) and stops the output of the transmission signal to save power. In this case, however, the hovering function of displaying the hover as a guide on the touchpanel is not effectively activated until the active stylus exits the sleep state and the output of the transmission signal is resumed.